This multi-center study seeks to determine the pharmacokinetics, maximum tolerated dose and long-term safety of ganciclovir in HIV-infected infants, children and adolescents (ages 2 weeks to 20 years) with CMV infection. This oral treatment would have important advantages for children being treated for CMV retinitis. Additionally, oral ganciclovir might prove useful for the prevention of CMV diseases in persons at risk.